Grain bins for storing various types of grain commonly include aeration systems to enhance drying of the grain within the bin. One type of aeration system comprises a perforated floor in the bin through which air is forced. Such aeration systems dry grain from the bottom up, which often leaves the grain in the center and top of the bin damp. Another type of aeration system is one or more horizontal tubes extending through the bin with holes in the tubes to provide drying air.
Another aeration system utilizes a centrally located vertical aeration tube extending upwardly from the bottom of the bin, with holes in the cylindrical tube wall to provide drying air to the grain in the bin. Such vertical tube aeration systems are typically used in grain bins having a sloped hopper bottom with a central discharge opening with a gate moveable between open and closed positions. One type of vertical tube aeration system known as the Grain Guard Rocket has a hollow center core to increase the amount of available air flow into the grain and to reduce the obstructive nature of the unit by allowing grain to flow downwardly through the hollow center during unloading of the bin. A significant problem with vertical aeration units is structural failure during unloading of the storage bin. When hopper bottom grain bins are unloaded, the downward movement of the grain exerts high forces on all surfaces which contact the grain. Thus, an aeration unit within the grain bin must be able to resist these forces under a variety of conditions, or be subject to structural failure.
There are two types of bulk grain material flow during unloading of hopper bottom bins, either funnel flow or mass flow. In funnel flow, the grain material forms a reverse cone as it is unloading and tends to draw from the center of the bin with the particulate material falling away from the side walls of the bin, rather than sliding down the side walls. In mass flow, the grain tends to unload without forming a reverse cone in the center, and the material moves downward in the bin in a mass form that creates much greater drag on the side walls of the in. The controlling factor to determine mass flow versus funnel flow is the slope of the bottom cone of the hopper bin. With grain, funnel flow normally occurs with hopper slopes of 45° or less, while mass flow occurs with hopper slopes of 50° or more. The actual angle at which the flow changes from funnel to mass is affected by the type of stored commodity and the rate of unload.
The “Rocket” vertical aeration systems sold by Edwards Grain Guard of Alberta Canada, normally perform well when installed in a hopper bin that stores common grain commodities, such as cereal grains, and the bin unloads with funnel flow. However, the failure rate is high when vertical units are installed in a steep cone hopper bin where mass flow is present. The structural failure arises, since the inside and outside walls of the hollow vertical tube do not have sufficient strength to resist the vertical forces that are created from the boundary layer drag during unloading. While the light gauge sheet metal used in conventional vertical aeration systems may survive the vertical forces as long as the unit remains absolutely vertical, these units are also subject to relatively high horizontal and bending forces during unloading. The physical weight of the grain against the walls of the vertical tube can create deformations that destroy the vertical alignment of the light gauge walls, and significantly reduce the load carrying capacity of the tube. Then, the walls are crushed and the structure fails.
Another problem with vertical bin aeration systems is the inability to retrofit such systems into existing bins. Typically, the sheet metal walls which form the cylindrical tube are factory assembled using rivets and self-drilled sheet metal screws, which are not reasonably feasible to field assembly within a bin. Therefore, the vertical aeration system must be installed at the time of original manufacture or assembly of the grain bin.
Accordingly, a primary objective of the present invention is the provision of an improved vertical aeration system for use in a hopper bottom grain bin.
Another objective of the present invention is the provision of an improved grain bin vertical aeration system having a pyramid frame to withstand the unloading forces of grain from the bin.
A further objective of the present invention is the provision of an improved grain bin vertical aeration system having concave walls which are subject to tensile forces, rather than compression forces, during unloading of grain from the bin.
Yet another objective of the present invention is the provision of an improved vertical aeration system for bottom hopper grain bins which will withstand vertical and horizontal unloading forces.
Still another objective of the present invention is the provision of an improved vertical aeration system for grain bins which can be mounted in bottom hoppers having varying angles of slope.
Another objective of the present invention is the provision of an improved vertical aeration system for grain bins which can be retrofit into existing grain bins.